In a semiconductor manufacturing process, a foreign matter on a semiconductor substrate (wafer) may cause a failure such as a failure in insulation of wiring and a short circuit thereof. With the progress of miniaturization of patterns on semiconductor devices, a minute foreign matter in a semiconductor substrate may cause a failure in insulation of a capacitor, breakage of a gate oxide film or the like.
Likewise, a liquid crystal display device manufacturing process involves existence of a foreign matter on a pattern or occurrence of some defects on a shape of the pattern. Such a foreign matter or defects will disable the use of the device as a display device.
Further, the above is true for the case of a manufacturing process of printed circuit boards. A foreign matter mixed in the manufacturing process may cause a short circuit in a pattern, and a poor connection thereof.
Patent Document 1 discloses an example of a technique for detecting a foreign matter on this kind of substrate. To be more specific, according to the technique disclosed in Patent Document 1, a semiconductor substrate is irradiated with laser light to detect scattered light from a foreign matter which adheres to the semiconductor substrate, and the scattered light is detected and the signal is compared with the inspection result of the same kind of semiconductor substrate which has been subjected to the immediately preceding inspection. Comparing the detected signal with the inspection result makes it possible to eliminate a false report caused by a pattern, thereby enabling inspection of a foreign matter and a defect with high sensitivity and high reliability.
In addition, as the technique for inspecting a foreign matter, there is known a method in which a wafer is irradiated with coherent light, and light radiated from a repetitive pattern on the wafer is removed by a spatial filter, and a foreign matter and a defect which do not have repeatability are emphasized to detect the foreign matter and the defect.
Moreover, Patent Document 2 discloses a foreign matter inspection system, wherein a circuit pattern formed on a wafer is irradiated from a direction inclined by 45° with respect to a main straight line group of this circuit pattern to prevent a zero-order diffracted light from the main straight line group from entering an aperture of an objective lens of a detection optical system.
Furthermore, Patent Document 3 discloses a technique in which the inspection sensitivity is improved by most suitably setting a spatial filter for each area on a wafer to perform inspection.